The highest-ranking US general in Iraq authorised the use of interrogation techniques that included sleep manipulation, stress positions and the use of dogs to "exploit Arab fears" of them, it emerged today.

A memo signed by Lieutenant General Ricardo Sanchez authorised 29 interrogation techniques, including 12 that exceeded limits in the army's own field manual and four that it admitted risked falling foul of international law, the Geneva conventions or accepted standards on the humane treatment of prisoners.

The memo, dated September 14 2003, also stated that the Iraq interrogation policy was modelled on the one used at Guantánamo Bay "but modified for applicability to a theater [sic] of war in which the Geneva conventions apply".

On Friday, a US court ordered the papers' release under the American Freedom of Information Act, following a request by the American Civil Liberties Union.

"The memo clearly establishes that Gen Sanchez authorised unlawful interrogation techniques for use in Iraq, and, in particular, these techniques violate the Geneva conventions and the army's own field manual governing interrogations," ACLU lawyer Amrit Singh said in a statement. "He and other high-ranking officials who bear responsibility for the widespread abuse of detainees must be held accountable."

The memo also authorised techniques to alter the environment of prisoners, such as adjusting temperatures or introducing unpleasant smells, in the full knowledge that "some nations may view application of this technique in certain circumstances to be inhumane". Another technique, called "fear-up harsh", aimed at "significantly increasing the fear level of a detainee", was also given the green light. Yelling, loud music and light control were also cleared "to create fear, disorientate [the] detainee and prolong capture shock".

The existence of the memo had been widely rumoured in the wake of the Abu Ghraib prison scandal over the abuse of detainees by US guards. The US administration has maintained any abuse was the result of improper individual action and was not sanctioned by leaders.

The memo also laid out guidance for when the controversial interrogation techniques could be used. It stated there should be "a reasonable basis to believe that the detainee possesses critical intelligence". Dogs should be muzzled and under the control of a military dog handler "to prevent contact with [the] detainee".

Gen Sanchez ordered that his personal approval should be gained before the most controversial techniques were used. He has denied that he gave that permission. The ACLU has a lawsuit pending against Gen Sanchez alleging direct responsibility for the torture and abuse of detainees in US military custody.

The Abu Ghraib scandal, in which US forces physically abused and sexually humiliated Iraqi prisoners at a jail on the outskirts of Baghdad, occurred on during Gen Sanchez's command. Gen George Casey replaced him as top commander in Iraq nine months ago.

The ACLU said the Pentagon initially refused to release the memo on national security grounds.